.calculator {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: 130px auto;
    grid-gap: 1px 1px;
    margin: 0 auto;
    width: 320px;
    height: 530px;
    background: #000;
}
.calculator-screen {
    display: flex;
    justify-content: flex-end;
    align-items: flex-end;
    grid-column: 1 / -1;
    padding: 20px;
    color: #fff;
    font-size: 4.5rem;
}

.calculator-button {
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 3.2rem;
    cursor: pointer;
    user-select: none;
}
.calculator-function {
    background: #bbb;
    border: 2px solid #bbb;
    color: #000;
}
.calculator-function:active {
    background: #aaa;
    border-color: #aaa;
}
.calculator-operator {
    background: #f97e0f;
    border: 2px solid #f97e0f;
    color: #fff;
}
.calculator-operator:active {
    background: #d96f0d;
    border-color: #d96f0d;
}
.calculator-number {
    background: #ddd;
    border: 2px solid #ddd;
    color: #000;
}
.calculator-number:active {
    background: #ccc;
    border-color: #ccc;
}
.calculator-zero {
    grid-column: 1 / 3;
}
.calculator-operator--active {
    border-color: #000;
}